In a screen printing device, since an upper surface of a screen mask is frictioned by a squeegee as a result of a squeegeeing action when screen printing is performed on an upper surface of a circuit board by placing a screen mask thereon, it is likely that the screen mask will become charged with static electricity. If the screen mask becomes charged with static electricity, in a case of performing screen printing on an upper surface of a circuit board on which an electronic component is mounted on a lower surface thereof, there is a possibility that the delicate circuits inside the electronic component, which are on a lower surface side of the circuit board, will break as a result of the discharge of the static electricity from the screen mask. In addition, even in a case of performing screen printing on an upper surface of a circuit board on which an electronic component is not mounted on a lower surface thereof, there is a possibility that the circuit board will become charged with static electricity as a result of the static electricity on a screen mask side transferring to the circuit board, which is contact with a lower surface of the screen mask, and that the delicate circuits inside an electronic component, which is subsequently mounted, will break.
In order to prevent such damage to an electronic component as a result of the discharge of static electricity from a screen mask, as disclosed in PTL 1 (JP-A-2004-17512), there are screen printing methods that are configured so that an earth line is connected between a mask holder that holds a screen mask, and an upper surface of the screen mask, and static electricity with which the screen mask is charged, is released to an earth side through the earth line and the mask holder, or static electricity is released from the screen mask as a result of bringing a destaticizing brush, which is connected to the earth side, into contact with the upper surface of the screen mask.
In addition, in a case in which a screen mask is formed of plastic, as disclosed in PTL 2 (JP-A-8-252988), there are screen printing methods that are configured so that a conductive layer is formed on both upper and lower surfaces of a screen mask, and static electricity is removed from the screen mask through the conductive layer and a clamp member that clamps a circuit board.